Cellulose sponges



. April 7, 1959 F. B. sTlEG 2,880,726

CELLULOSE SPONGES Filed Jan. 4, 1954 CELLULOSE SPONGES Fred B. Stieg, Jackson Heights, N.Y.

Application January 4, 1954, Serial No. 402,107

13 Claims. (Cl. 12S-285) This invention relates to synthetic sponges, particularly sponges formed of regenerated cellulosic material, as Well as to articles made of such Sponges.

While various forms of regenerated cellulosic Sponges havebeen proposed and certain of these have been commercially used, these known types of regenerated cellulose Sponges have been found to be feasible only for a limited number of uses, both from a purely physical viewpoint and also from an economic standpoint. In some instances, the known types of cellulose sponges have not been well adapted to articles or uses wherein aligned bres, for example, surgical cotton, have been widely used. Another difficulty experienced with presently known synthetic Sponges has been the inability to properly balance or proportion their dimensional stability, liquid absorbency, desired firmness when dry with desired softness when wet, mechanical strength, rapidity of liquid absorbency and liquid retention under slight or moderate compression.

It is an object of the present invention to overcome the foregoing disadvantages and difculties of known cellulosic Sponges and to provide `Sponges having characteristics suitable for a wide variety of uses. Other objects and advantages of the invention will be in part apparent and in part pointed out hereinafter.

In one of its broader aspects, the invention may be said to lie in providing a regenerated cellulose sponge of extremely high porosity. In another aspect the invention may be said to lie in providing a sponge of such high porosity, which has good mechanical strength without the addition thereto of fibres to reinforce the regenerated cellulose. In still another aspect the invention may be said to lie in providing regenerated cellulose Sponges which contain significant amounts of powdered or comminuted cellulosic material, preferably highly purified cellulose which is commonly called alpha cellulose. In still another aspect, the invention may be said to lie in providing a sponge comprised of highly purified, bleached and sterile cellulose.

Before describing my invention in detail, it is to be understood that reference to specific embodiments of my invention is primarily intended to aid in illustrating the United States Patent C) features and advantages of the invention but is not ingrated or shredded to form alkali cellulose crumb. The

alkali cellulose crumb is next treated with carbon disulfide to form cellulose xanthate. To this is added dilute NaOH solution to yield a .viscose solution containing'from HCC 4% to 6% cellulose in the form of xanthate and about In one procedure, where powdered or comminuted cellulose material, as Such, is a part of the articles to be formed, the comminuted cellulose is dispersed in the aforesaid 4% to 6% cellulose, 6% NaOH, viscose solution.

In another procedure, wherein mercerized powdered or comminuted cellulose material is to be a part of the nal article, the viscose solution is made as heretofore described except that the initial cellulose content of the viscose will be about 8%. 'I'he powdered cellulose is separately mercerized with about 9-10% caustic soda; enough soda is used so that when itis later diluted with water to a caustic strength of about 6% and added to the viscose solution, the cellulose concentration (in the form of xanthate) of the final mixture is from 4% to 6%.

To the viscose mixtures described above I add line crystals of a hydrated compound such as the dodecahydrate of trisodium phosphate or the decahydrate of sodium sulfate. While I find that in conducting the regeneration of the cellulose from the viscose mixture, the trisodium phosphate permits an initial regeneration temperature of about -80 C., thus minimizing degeneration of the cellulose, still good results are to be obtained with the sodium sulfate even though a higher regenerating temperature is needed.

In making the paste of crystals and viscose mixture it is important to ensure that the crystals are quite fine and not agglomerated. Crystals which will pass a 30 mesh screen or liner are satisfactory.

Thereupon the paste is cast into molds or continuously extruded and the cellulose portion of the viscose solution in the paste regenerated by heat as indicated above, the heat being maintained for about 5A to one hour in order to minimize cellulose degeneration and gasification which tends to yield large pores. Thereupon the partially regenerated cellulose is steamed to complete the regeneration. As a final step the nal sponge product is washed and thereafter may be bleached or otherwise purified or even dyed.

In making the particular paste described, the cellulose subjected to the l8-20% caustic soda `Solution and carbon disulfide has an intrinsic viscosity of about l0 and greater whereas the powdered or comminuted cellulose has a signilicantly lower intrinsic viscosity, for example, about 4.5 or less. Both forms of cellulose used were highly purified and bleached to a high degree of whiteness. Celluloses derived from Wood are generally found satisfactory for the above purposes although of course other Sources of high grade cellulose may be used. n

In making Sponges according to the invention, one may vary the proportions of the cellulose xanthate to the powdered cellulose over a wide range, dependent upon the properties desired to be incorporated into the final product. For example in certain instances as much as one half or more of the final product sponge will be comprised of powdered cellulose, either mercerized or unmercerized.

The purely physical distinctions between Sponges made as described above and the currently typical commercial Sponges of regenerated cellulose and hemp, flax, hair, man-made fibres or the like, all of substantial length, may perhaps best be appreciated by reference to the accompanying drawings wherein:

Figure 1 is a reproduction of a photograph, about 13 diameters actual size, of a dry extra fine textured sponge made according to the invention, the photograph having been taken of a specimen cut along its longest axis.

Figure 2 is a view similar to Figure l except the extra fine sponge is viewed when wet.

Figure 3 is a view of the wet sponge of Figure 2 but taken at right angles to the plane of Figure 1.

Figure 4 is a perspective view of a vaginal tampon made according to an embodiment of the invention.

The conventional regenerated Sponges containing hemp, flax, hair, man-made bres or the like, even when made in the so-called commercial tine textures, are considerably coarser than sponges made according to the invention. Moreover, the conventional Sponges are somewhat non-homogeneous in that their porosity differs depending upon which section is viewed and with a wide variance of pore sizes in any section. This renders them less uniform in mechanical strength as well as in other properties. In contrast, a sponge made according to the invention as illustrated in Figures 1, 2 and 3 is quite homogeneous in its porosity and free from the very large pores which characterize known Sponges.

It is to be noted that sponges made according to the invention may be so porous that, when dry, each cubic inch thereof contains about 1,400,000 voids and, when wet, so that its volume expands to some 200% of the original volume, the number of voids is approximately 500,000 to 700,000 per cubic inch.

In Figure 4 is shown a tampon generally designated as 11 which has a typically cylindrical form 13 and a smoothly rounded end 15. Through an aperture 16 near the opposite end of tampon 11 is passed a small string 17 so that the user may conveniently remove the tampon from the vagina. As shown, the cylindrical surface 14 of tampon 11 is knurled to increase the rate of wetting although such knurling is not essential for good performance. It is to be noted that a tampon as illustrated need not have an enveloping support for insertion, such as the cylindrical telescoping tubes used with conventional cotton tampons; on the contrary tampon 11 has suicient firmness when dry so that the user may easily insert the tampon into the body cavity. The elimination of supporting tubes makes it possible to manufacture tampons according to the invention rather simply and without the added packaging expense entailed by the use of supporting tubes of conventional tampons. Also when moderately Wet and resilient they can be inserted without using an added mechanism.

In casting or molding a tampon such as is illustrated in Figure 4, one makes up a paste comprised of viscose, with or without highly purified comminuted cellulose, and crystals as described above. This paste is placed in molds having the general outline of the desired tampon and subjected to conditions such as heat which will regenerate the cellulose of the cellulose xanthate. In a typical example about 2.553 cubic inches of paste are cast into a tampon mold; when dried the iinal tampon formed has a volume of only 0.393 cubic inch. When crystals passing a 40 mesh screen are used, the final tampon has about a million and a half voids or pores per cubic inch.

A signicant feature of the Sponges made according to my invention is their dimensional stability or dimensional memory particularly when wet. For example, when a tampon made of one of my Sponges is in use, in the wetted condition (which occurs rapidly, as pointed out hereinafter), the tampon is soft, resilient and smooth to the touch. As the user walks, sits, rises or otherwise moves, the easily deformable sponge tampon accommodates itself to the actions of the user without discomfort. While a conventional cotton tampon also is deformed when wet, it exhibits little tendency to return to its original shape, rather remaining as the soggy wad of common experience. This feature of my Sponges is of importance inasmuch as when they are momentarily squeezed or deformed and a minor quantity of sorbed liquid expelled, upon the release of the deforming pressure, the sponge promptly assumes its original shape i.e. it remembers its original dimensions and re-sorbs any expelled liquid. In contrast, the gross absorbent characteristic of the conventional tampon is diminished with more or less severity depending upon the extent of deformation. As may readily be perceived, such diminution of gross absorbency and failure to reabsorb expelled liquid, characteristic of conventional tampons, is undesirable and in use may result in embarrassing and unexpected leakage from the body cavity.

In order to demonstrate more clearly the advantageous characteristics of Sponges made according to the invention, there is tabulated below a comparison of certain physical characteristics of the new Sponges (cast in the form of a tampon) with three conventional commercial Sponges cut into a tampon form and with two commercial brands of cotton tampons. In this tabulation S2 and S3 refer respectively to my sponges made of 58% regenerated viscose cellulose with 42% unmercerized comminuted purified cellulose and 58% regenerated viscose cellulose with 42% mercerized comminuted purilied cellulose. The physical dimensions of these pieces when dry are as follows:

S2 2 x 1/2, weight 1.6 gms., vol. .3927 in.3 S3 2" x 19/32", Weight 1.6 gms., vol. 0.5552 in.3

The dry commercial cotton tampons, designated as T and M respectively, are 11/2" x 1/2, 2.2 gms. 0.2945 in 3, and 1% x 1/2", 2.5 gms., 0.3436 in. The commercial sponges were cut into tampon form from rectangular blocks, three samples of each sponge being cut, one along the longest axis, one along the intermediate axis and one along the shortest axis. These samples are designated as DSF, DIF and DLF the subscripts indicating that a sample D was cut along the short axis S, the intermediate axis I or the long axis L and the general porosity was F for ne. Similarly a sample labeled DLC means it was a commercial sponge D cut along the long axis and was of C or coarse grade. The letter N designates another commercial brand of sponge containing some synthetic man-made iibre in addition to flax, hemp or hair. The dry dimensions of these Sponges are as follows:

DSC 2 x 1/2", 0.4 gm., 0.3927 in.3 DIC 2l x 1/2, 0.4 gm., 0.3927 in.3 DLC 2" x 1/2", 0.4 gm., 0.3927 in.3 DSF 2" x 1/2", 0.4 gm., 0.3927 in.3 DIF 2" x 1/2, 0.4 gm., 0.3927 in.3 DLF 2 x 1/2", 0.4 gm., 0.3927 in.3 NSC 2 x 1/2, 0.3 gm., 0.3927 in.3 NIC 2" x 1/2", 0.3 gm., 0.3927 in 3 NLC 2 x 1/2, 0.3 gm., 0.3927 in.3

The results of comparative tests are set forth below in Tables I, II, III. Such tests include a hydrostatic pressure test wherein each sample was subject to one p.s.i. hydrostatic pressure and its characteristics noted. This test simulates the conditions of normal or abnormal pressures in the human vagina. Additional tests were a saturation test, absent any superimposed pressure, a tensile strength test and a rate of wetting or absorbency test, termed a wicking test.

TABLE I 1 lb. p.s.. hydrostatic pressure Time Water Vol. in- (sec.) for Water pickup crease, Sample water pickup per dry percent;

passage (gms.) in. dry to through wet 59 8. 5 21. 6 195 20 10. 3 18. 5 179 69 6. 6 22. 4 188 71 7. 7 22. 3 178 16 3. 0 7. 6 125 13 2. 3 5. 8 177 18 2. 2 5. 6 171 13 3. 5 8. 9 146 21 2. 9 7. 4 177 14 2. 8 7. 1 166 55 3. O 7. 6 155 35 3. 5 8. 9 177 NLC 3. 2 8. 2 166 5 TABLE n Saturation test Vol. 1n- Satu- Water Saturated crease Sample rated pickup volume (wet to (gms.) (gms.) (in.) saturated) (percent) 15. 8 14. 2 0. 7670 None 15. 8 14. 2 0. 9940 None 17. 14. 8 0. 9844 178 16. 8 14. 3 1. 0209 167 .5. 8 5. 4 0. 4909 None '6.5 6. 1 0. 6947 None `6. 9 6. 5 0. 6711 None 7. 7. 1 0. 5747 None 8. 4V. 8. 0 0. 6947 None .9. 2 8. 8 0. 6520 None 7. 2 6. 9 0. 6113 None 6. 7 6. 4 0. 6947 N one 6. 5 6. 2 0. 6523 N one In Table III is set forth the comparative wet tensile strength as measured lengthwise and the wicking time of the various samples. The wicking time was measured by noting the elapsed time between initial wetting of the bottom of a dry sample tampon and wetting of the top end when the tampon is maintained upright. All samples As indicated by the above comparisons, the several sponges made according to the invention have sorbency characteristics far superior to commercial regenerated cellulose fibre sponges and at least of the same calibre as cotton tampons. The strength thereof is more uniform and the speed of wettingv is far superior to commercial sponges. Furthermore, the characteristics of my sponges may be adjusted or varied to meet the needs of particular uses, for example, by varying the proportions of xanthate and comminuted cellulose or by using mercerized or unmercerized comminuted cellulose.

So that those skilled in the art may be guided as to how to adjust the composition of sponges according to the invention to meet particular uses, the following sets forth the general effect of particular variations. For example, increasing proportions of comminuted cellulose tend to: (a) decrease the tensile strength and water pickup expressed in volumes per volume of the sponge; (b) increase dimensional stability from wet to dry and dry to wet (i.e. less swelling from dry to wet); (c) increase the rate of water pickup on a weight basis; and (d) make the tensile strength more uniform in all directions. In addition, sponges made with mercerized comminuted cellulose tend to shrink less from the mold upon regeneration than do sponges containing unmercerized comminuted cellulose.

While I have particularly described my invention when used as a tampon, it is to be noted that one may make somewhat finer or coarser sponges as described. The sponge also may be used for a wide variety of purposes, with or without added ingredients such as powdered materials, abrasives, medicaments, deodorants and the like. In addition, sponges as set forth above may be used as absorbers or lters for other liquids such as gasoline and the like or as iilters for gases and gaseous dispersions such as fogs and smokes. One may make advantageous use of my sponges as iilters for cigarettes, pipes and the like.

Having now particularly described my invention, what is claimed is:

1. A sponge comprised of a major quantity of regenerated cellulose and a minor quantity of finely comminuted l-highly purified unregenerated cellulose, said sponge containing a multiplicity of line pores to the extent of at least 500,000 pores per cubic inch.

2.v A sponge comprised of regenerated cellulose and a significant quantity of finely comminuted highly puried unregenerated cellulose.

3. A sponge comprised of regenerated cellulose and a significant quantity of nely comminuted highly purified unregenerated cellulose, said sponge containing at least 500,000 pores per cubic inch.

4. A sponge comprised of regenerated cellulose and a significant quantity of finely comminuted highly puried unregenerated cellulose, the unregenerated cellulose used having an intrinsic viscosity of not more than 4.5.

5. A sponge comprised of regenerated cellulose and a significant quantity of finely comminuted highly puriiied unregenerated cellulose, said unregenerated cellulose being mercerized.

6. A sponge comprised of regenerated cellulose and a signicant quantity of nely comminuted highly purified unregenerated cellulose, said unregenerated cellulose being fine enough to pass a standard 20 mesh screen.

7.xA sponge comprised of regenerated cellulose and a significant quantity of nely comminuted highly puriiied unregenerated cellulose, said unregenerated cellulose having been bleached to whiteness.

8L A sponge according to claim 7 wherein said regenerated cellulose has been bleached to whiteness.

9. A tampon comprised of a iirm dry sponge containing a major quantity of regenerated cellulose and a minor quantity of powdered highly puried unregenerated cellulose.

10. A tampon comprised of a firm dry sponge containing a major quantity of regenerated bleached cellulose and a minor quantity of powdered. highly purified bleached unregenerated cellulose.

1l. A tampon according to claim 9 wherein said sponge contains at least 500,000 pores per cubic inch.

1,2. A tampon according to claim 10 wherein at least one'outer surface thereof is knurled.

13. A tampon according to claim 9 wherein the outer surfaces thereof are free from protruding fibres.

References Cited in the tile of this patent UNITED STATES PATENTS 1,611,056 Mostny Dec. 14, 1926 2,254,272 Crockford Sept. 2, 1941 2,295,823 Banigan et al. Sept. 15, 1942 2,341,509 Bley Feb. 15, 1944 2,706,159 Kreek et al Apr. 112, 1955 

1. A SPONGE COMPRISED OF A MAJOR QUANTITY OF REGENERATED CELLULOSE AND A MINOR QUANTITY OF FINELY COMMINUTED HIGHLY PURIFIED UNREGENERATED CELLULOSE, SAID SPONGE CONTAINING A MULTIPLICITY OF FINE PORES TO THE EXTENT OF AT LEAST 500,000 PORES PER CUBIC INCH. 